High-resolution mass spectrometer and methods for determining the isotopic anatomy of organic and volatile molecules

Abstract

A mass spectrometer including an entrance slit, an energy filter, a momentum filter and a detector array, the entrance slit, energy filter and momentum filter being configured to provide molecular analyte ions to the detector array at a mass resolution of about 20,000 or greater. A method for determining the isotopic composition of an analyte in a sample includes converting the analyte to molecular analyte ions, separating the molecular analyte ions using an entrance slit, separating the molecular analyte ions according to their energy levels, separating the molecular analyte ions according to their momenta, detecting two or more of the molecular analyte ions at a mass resolution of about 20,000 or greater to produce molecular analyte ion data; and analyzing the molecular analyte data to determine the isotopic composition of at least a portion of the analyte.

What is claimed is: 
     
       1. A mass spectrometer comprising:
 an entrance slit having a width, the slit configured to guide a first output of molecular analyte ions along a path, the molecular analyte ions of the first output having energy levels; 
 an energy filter positioned along the path downstream from the entrance slit and configured to receive the first output of molecular analyte ions, the energy filter having a first radius of curvature along the path, the energy filter configured to filter the molecular analyte ions of the first output according to their energy levels and produce a second output of molecular analyte ions; 
 a momentum filter positioned downstream from the energy filter and configured to receive the second output of molecular analyte ions, the momentum filter having a second radius of curvature along the path, the momentum filter configured to filter the molecular analyte ions of the second output according to their momenta and produce a third output of molecular analyte ions, the third output of molecular analyte ions comprising at least two ion beams; and 
 a detector array positioned downstream of the momentum filter and configured to receive the third output of molecular analyte ions and resolve and concurrently detect the at least two ion beams, 
 wherein the width and the first and second radii of curvature are selected to provide a mass resolution at the detector array of 20,000 or greater. 
 
     
     
       2. The mass spectrometer of  claim 1 , wherein respective molecular analyte ions of the at least two ion beams have respective masses that differ from one another by about 1 atomic mass unit, and
 wherein the width, the first and second radii of curvature, and the detector array are configured to resolve and concurrently detect the at least two ion beams at the detector array and to distinguish between molecular analyte ions within each ion beam at one part in 20,000. 
 
     
     
       3. The mass spectrometer of  claim 1 , wherein the third output of molecular analyte ions comprises at least two molecular analyte ions, respective masses of the at least two molecular analyte ions being the same when rounded to the nearest whole number, the width and the first and second radii of curvature are configured to resolve the at least two molecular analyte ions at the detector array, and the detector array is configured to concurrently detect the at least two molecular analyte ions. 
     
     
       4. The mass spectrometer of  claim 1 , wherein the width is about 5 μm to about 250 μm, the first radius of curvature is about 20 cm to about 25 cm, and the second radius of curvature is about 20 cm to about 25 cm. 
     
     
       5. The mass spectrometer of  claim 1 , wherein the width is about 5 μm, the first radius of curvature is about 22 cm and the second radius of curvature is about 23 cm. 
     
     
       6. The mass spectrometer of  claim 1 , further comprising an ion source along the path upstream from the entrance slit and configured to provide an electron impact energy of about 5 eV to about 150 eV and to provide the first output of molecular analyte ions to the entrance slit. 
     
     
       7. The mass spectrometer of  claim 6 , wherein the ion source is configured to provide an electron impact energy of about 25 eV to about 150 eV. 
     
     
       8. The mass spectrometer of  claim 1 , further comprising an ion source along the path upstream from the entrance slit and capable of providing an electron impact energy of less than 50 eV and configured to provide the first output of molecular analyte ions to the entrance slit. 
     
     
       9. A method of identifying a potential oil-field, the method comprising:
 analyzing an analyte of a sample from a target field using the mass spectrometer of  claim 1  to obtain molecular analyte ion data: 
 analyzing the molecular analyte ion data to obtain the isotopic composition of at least a portion of the analyte to determine relative proportions of at least a portion of isotopologues in the sample; and 
 comparing the relative proportions of the isotopologues of the analyte to a database. 
 
     
     
       10. The method of  claim 9 , wherein the analyte is a hydrocarbon. 
     
     
       11. The method of  claim 10 , wherein the hydrocarbon is selected from the group consisting of methane, ethane, propane, butane, pentane and hexane. 
     
     
       12. A method of analyzing a drug or a drug metabolite, the method comprising:
 analyzing a drug or drug metabolite in a sample using the mass spectrometer of  claim 1  to convert the drug or drug metabolite to molecular analyte ions and to obtain molecular analyte ion data; 
 analyzing the molecular analyte ion data to obtain the isotopic composition of at least a portion of the drug or drug metabolite; and 
 comparing the isotopic composition obtained for the drug or drug metabolite to a database of isotopic compositions. 
 
     
     
       13. A method of determining an amount of an anthropogenic contribution to an atmospheric concentration of an atmospheric gas, the method comprising:
 analyzing an analyte of a sample using the mass spectrometer of  claim 1  to obtain molecular analyte ion data; 
 analyzing the molecular analyte ion data to obtain the isotopic composition of at least a portion of the analyte; and 
 comparing the isotopic composition obtained for the analyte to a database of isotopic compositions. 
 
     
     
       14. The method of  claim 13 , wherein the analyte is selected from the group consisting of methane, carbon dioxide, sulfates, hydrocarbons, noble gases, H 2 , O 2 , N 2 , NO and N 2 O. 
     
     
       15. The method of  claim 13 , further comprising determining a limit on anthropogenic emissions of the gas based on a correlation between the isotopic composition obtained for the analyte and the database of isotopic compositions. 
     
     
       16. A method for the diagnosis or treatment of a disease, the method comprising:
 analyzing an analyte of a sample from a patient using the mass spectrometer of  claim 1  to obtain molecular analyte ion data; 
 analyzing the molecular analyte ion data to obtain the isotopic composition of at least a portion of the analyte; and 
 comparing the isotopic composition obtained for the analyte to a database of isotopic compositions. 
 
     
     
       17. A method for determining a prior temperature of a sample, the method comprising:
 analyzing an analyte of the sample using the mass spectrometer of  claim 1  to obtain molecular analyte ion data; 
 analyzing the molecular analyte ion data to obtain the isotopic composition of at least a portion of the analyte; and 
 comparing the isotopic composition obtained for the analyte to a database of isotopic compositions. 
 
     
     
       18. The method of  claim 17 , wherein the prior temperature is a temperature at which the sample was formed.